Visibility.js
Visibility.js allows you to determine whether your web page is visible to a user, is hidden in background tab or is prerendering. It allows you to use the page visibility state in JavaScript logic and improve browser performance by disabling unnecessary timers and AJAX requests, or improve user interface experience (for example, by stopping video playback or slideshow when user switches to another browser tab).
Tock
Timer Object/Class. Kickass!
Supermodel
Supermodel - Minimal Model Tracking for Backbonejs
Modernizr
Modernizr is a JavaScript library that detects HTML5 and CSS3 features in the user’s browser.
Rambda
Faster alternative to Ramda in just 10kB
Webshim
Webshims Lib is a modular capability-based polyfill-loading library
Radio
Dependency-free Chainable Publish/Subscribe Library for Javascript
Q
A tool for making and composing asynchronous promises in JavaScript
Backbone Layout Manager
A layout and template manager for Backbone.js applications.
UA Parser
Lightweight JavaScript-based User-Agent string parser. Supports browser & node.js environment. Also available as jQuery plugin.
Backbone.stickit
Backbone data binding, model binding plugin. The real logic-less templates.
Autolink Js
Tiny little tool to find URLs in a string of text and hyperlink them
PreloadJS
PreloadJS makes preloading assets & getting aggregate progress events easier in JavaScript. It uses XHR2 when available, and falls back to tag-based loading when not.
Csso
CSS-optimizer
Sticky Kit
A jQuery plugin for creating smart sticky elements
Stampit
Create objects from reusable, composable behaviors.
Machina.js
js ex machina - finite state machines in JavaScript